Phase-change materials (PCM) are capable of transforming from a crystalline phase to an amorphous phase. These two solid phases exhibit differences in electrical properties, and semiconductor devices can advantageously exploit these differences. Given the ever-increasing reliance on radio frequency (RF) communication, there is particular need for RF switching devices to exploit phase-change materials. However, the capability of phase-change materials for phase transformation depends heavily on how they are exposed to thermal energy and how they are allowed to release thermal energy. For example, in order to transform into an amorphous state, phase-change materials may need to achieve temperatures of approximately seven hundred degrees Celsius (700° C.) or more, and may need to cool down within hundreds of nanoseconds.
Heating elements in PCM RF switches and connections for the heating elements often create parasitics associated with RF frequencies, and result in performance tradeoffs. Fabricating connections for both PCM and heating elements without significant RF performance tradeoffs, such as tradeoffs involving insertion loss and OFF state parasitic capacitance (COFF), becomes complex, especially where the RF switch is designed primarily around thermal performance. Accordingly, accommodating PCM in RF switches can present significant manufacturing challenges. Specialty manufacturing is often impractical, and large scale manufacturing generally trades practicality for the ability to control device characteristics and critical dimensions.
Thus, there is a need in the art to simply and reliably manufacture low parasitics PCM RF switches, and in particular RF switches with reduced insertion loss and reduced OFF state parasitic capacitance (COFF).